The search was BEFORE discovery of an outstanding arrest warrant? Sounds like Thomas is saying the search was reasonable because it was AFTER the arrest.
Well, I took the bold and daring step of actually reading part of the opinion. Clever, huh?
You are right that the search took place after the cop had stopped the guy and found out he had an arrest warrant out on him. At that point the search was a search incident to a valid arrest, for which no separate search warrant is needed.